This invention relates to an authentication system, in particular, a system for detecting impersonation made by a person entering/exiting from a room.
In recent years, there has been a growing need for security management conducted when people enter/exit a security zone with a growing interest in security issues including an increasing crime rate. Therefore, there is a high demand for more reliable security products. A room entry/exit management system mainly uses a method of reading a non-contact-type card or a contact-type card held by a subject through a card reader. Further, there is also a room entry/exit management system for performing authentication based on a facial image of the subject.
On the other hand, there is proposed a facial image retrieval system in which an image is retrieved with high reliability by using photographing time of the image. For example, JP 2007-102517 A discloses a method of recognizing a face by storing a prediction coefficient corresponding to time passing after a face is registered until the face is photographed and performing an arithmetic operation on a feature amount for predicting the time passing after the face is registered until the face is photographed.
Further, JP 2010-238181 A discloses a technology whose object is to “improve authentication precision for a face” and which includes: “a facial database storing section 5 for storing a plurality of pieces of registrant image data, which are image data on a facial portion of a registrant, by an orientation and a size of the registrant's face within the registrant image data; a face detecting section 1 for detecting the facial portion of a person included in the image data from the obtained image data; a facial feature point extracting section 2 for extracting a feature point of the person's face from the obtained facial image data which is the image data on the detected facial portion of the person; a facial orientation/size estimating section 3 for estimating the orientation and the size of the person's face within the obtained facial image data; a facial authentication section 4 for authenticating whether or not the person's face is the registrant's face from the registrant image data and the obtained facial image data; and an authenticated image updating section 6 for storing the obtained facial image data in the facial database storage section 5 as the registrant image data when the person's face is authenticated as the registrant's face by the facial authentication section 4 (see Abstract of JP 2010-238181 A).
However, the above-mentioned method disclosed in JP 2007-102517 A raises a problem in that precision of verification cannot be enhanced because the verification is performed against previously registered image data instead of against recent facial image data and a problem in that processing time for verification increases as the facial image data increases.
Further, with the technology disclosed in the above-mentioned JP 2010-238181 A, facial images continue to be accumulated in principle excluding a case where there is no free space in a memory area. Therefore, a deviation occurs between a current facial image of a user and the facial images accumulated within a database, or the facial images accumulated within the database have a biased tendency, which may deteriorate the authentication precision. If the authentication precision deteriorates, a risk of impersonation becomes high, which is not desired from the viewpoint of security.
An object of this invention is to issue an alarm to an administrator at high speed and with satisfactory precision based on a result of searching a facial image database in a case where a user uses a card to enter/exit a room.